Here's where a clear distinction must be made regarding the definitions of the words "overweight" and "fat". The Body Mass Index, or BMI, is the ratio of one's bodyweight and height (i.e., kg/m^2). BMI has been widely recognized as the parameter for defining whether one is underweight (BMI<18.5), normal weight (BMI between 18.5 and 24.9), overweight (BMI between 25 and 29.9), obese (BMI between 30 and 39.9), or morbidly obese (BMI greater than 40). Thus, having a BMI greater than 25 but less than 30 is technically considered to be overweight. But here's the rub: people with more than average amounts of lean body mass (i.e., muscle) will most likely have BMI's greater than 25. This is because muscle, with its relatively high density, weighs much more than fat within the frame of a muscular person. So can muscular people be overweight? Yes, when speaking within the confines of the BMI definition. If muscular people are typically considered overweight, does this mean they are fat? Of course not! Fat, like muscle, is simply a tissue within the human body aside from lean body mass that makes up one's body composition. One can be overweight but lean due to a high proportion of muscle with relatively low bodyfat. If we can agree a muscular person is a fit person, then we can also agree an overweight person can be fit. So yes,one can be fit and overweight. Can one be fit and fat? This boils down to proportion and the definition of fat which is highly ambiguous. In general, a male and female is considered to be fat when bodyfat is above 20% and 30%, respectively. Being fat, or at least fatter than average, does not necessarily mean being overweight. Once again, this is because fat is not a dense tissue and one can be over-fat but still have a relatively low body weight. But being over-fat is generally not healthy because fatness does not predispose one to being fit (note: there are exceptions such as endurance swimmers who need more fat for insulation, buoyancy, and long-term energy). So yes, one can be fit and fat but this is more the exception (i.e., endurance swimmers) rather than the norm. The health risks of being fat are numerous (i.e., heart disease, stroke, diabetes, hypertension, etc.). Nevertheless, studies have shown that those people who were fat but maintained their aerobic fitness capacity were less likely to die from heart disease or stroke than those who were less fit. In other words, overweight or even obese people who became fitter fared as well or better in terms of life expectancy than leaner people who became less fit. The key message here is that increasing physical activity is likely to be at least as important as weight loss for reducing premature mortality. Here are the most common misunderstandings within our society and the key to this blog post when it comes to body weight and fitness:

You can be overweight and not fat--and be fit (a fit, nonfat overweight person)

You can be underweight and fat--and not be fit(!) (a non-fit, fat underweight person)

The first point is a healthy means of existence and may increase life expectancy whereas the latter point is not and may lead to premature mortality. If you exercise regularly by incorporating resistance training and cardio, you will most likely fall within the first group. If you are mostly sedentary, you may fall within the second group. Exercise, which can build muscle mass and decrease fat mass, is the key to being fit and living a healthy life.

BOTTOM LINE: Body weight is less relevant than fatness when it comes to fitness and longevity. Studies have shown that But no matter whether you are overweight or overfat, the important thing is to be fit if you want to live a longer life.

Brian Danley, CFT"Motivation is what gets you started. Habit is what keeps you going."

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I'm a personal trainer who loves to help others fulfill their health and fitness goals. I consider myself a bodybuilder in that I live the lifestyle of eating healthy food, working out regularly, and sculpting my body.